Traditional on-board vehicle equipment allows a user to receive and initiate telephone calls using a vehicle's on board equipment. The telephone user, often the driver, uses such an on-board telephone in hands-free speaker mode. With the proliferation of portable media devices in modern day society, it is common for passengers to use their portable devices in the vehicle. Audio output from such portable devices interferes with the telephone call and makes it very difficult to conduct the telephone call in hands-free speaker mode. When a call is initiated or received, the telephone participant must request each participant to pause or mute the audio playback of their portable media devices. Thus, traditional systems fail to provide the user with an efficient and seamless way to prevent the audio output from all portable devices within the vehicle from interfering with a telephone call that is in progress.